A contract year for Cam Thomas with the Chargers could be the last year.

That is the direction, anyway, the situation appears ahead.

The fourth-year veteran nose tackle has been replaced in San Diego's starting lineup, Sean Lissemore getting the nod Sunday versus the Giants. Lissemore joined the Chargers on a September trade with the Cowboys for a conditional draft pick, and he is under team control in 2014.

Thomas is not. This is the final year of the 2010 fifth-round pick's rookie deal.

He said Tuesday his approach to the rotation change is to "take it like a man."

"Come ready to play," Thomas said. "Basically, no difference in my mindset. Everything is competition. You just keep going. Keep building. We're out here trying to do something."

Lissemore's promotion was decided in the aftermath of the team's loss to the Bengals one week earlier.

Cincinnati rushed for 164 yards, including 101 in the second half. To ice the game, it chewed 35 yards on eight straight runs, burning three timeouts with three first downs.

This is a rotation change, not a benching.

Thomas, who's made 10 of his 15 career NFL starts this year, played a season-low 17 defensive snaps Sunday against New York. But that was only three fewer than Lissemore.

When asked about Lissemore, defensive coordinator John Pagano said Tuesday he was "very excited" about the 26-year-old.

"His play has really gotten better once he got into the system and what what (defensive line coach) Don Johnson has done with him," Pagano said. "He is a guy that can play the nose or at the end for us. He's a hard worker and disciplined player that is very structured in his game. He needs to keep getting better like everyone, but I thought he played well last week."

In Dallas, Lissemore fell on the short end of an offseason scheme change.

The Cowboys went from a 3-4 to 4-3 alignment, the latter a lesser fit for his skill set. Rather than cut him after the preseason, they traded him to San Diego for a conditional seventh-round draft pick in 2015.

In joining the Chargers' 3-4, Lissemore needed to regain some of the weight he lost and learn a new language. He did both.

A listed defensive end, he said it'd been a while since he last played so much nose tackle in one game, adding it "went well."

"It's a physical, physical position," Lissemore said. "I always pride myself on being a physical player, but pretty much any position on the defensive line is physical. ... Nose is like stepping into an intersection. You never know where you're going to get hit from. It's tough, but it's fun."